html{
	height: 100%;
}
body{
	margin: 0;
	padding: 0;
	font-family: sans-serif;
    background: linear-gradient(#00BFFF,#513de2);
}
.login-box{
	position: absolute;
	top: 50%;
	left: 50%;
	width: 400px;
	padding: 40px;
	transform: translate(-50%,-50%);
	background: rgba(0,1,0,.5);
	box-sizing: border-box;
	box-shadow: 0 15px 25px rgba(0,0,0,.6);
	border-radius:10px ;
}

/*login样式*/
.login-box h2{
	margin: 0 0 30px;
	padding: 0;
	color: #00BFFF;
	text-align: center;
}

/*相对定位*/
.login-box .user-box{
	position: relative;
}

/*input*/
.login-box .user-box input{
	width: 100%;
	padding: 10px 0;
	font-size: 16px;
	color: #fff;
	margin-bottom:30px ;
	border: none;
	border-bottom: 1px solid #fff;
	outline: none;
	background: transparent;
}
.login-box .user-box label{
	position: absolute;
	top: 0;
	left: 0;
	padding: 10px 0;
	font-size: 16px;
	color: #fff;
	pointer-events: none;
	transition: .5s;
}
.login-box .user-box input:focus ~ label,
.login-box .user-box input:valid ~ label{
	top: -20px;
	left: 0;
	color: darkblue;
	font-size: 12px;
}

.login-box form a{
	position: relative;
	display: inline-block;
	padding: 10px 20px;
	color: turquoise;
	font-size: 16px;
	text-decoration: none;
    text-transform: uppercase;
    overflow: hidden;
    transition: .5s;
    margin-top: 40px;
    letter-spacing: 4px;
}

.login-box form a:hover{
	background: turquoise;
	color: #fff;
	border-radius: 5px;
	box-shadow: 0 0 5px #00BFFF,
	            0 0 25px #00BFFF,
	            0 0 50px #00BFFF,
	            0 0 100px #00BFFF;
}

.login-box a span{
	position: absolute;
    display: block;
}
.login-box a span:nth-child(1){
	top: 0;
	left: -100%;
	width: 100%;
	height: 2px;
	background: linear-gradient(90deg, transparent,#03e9f4);
	animation: bth-anim1 1s linear infinite;
	
}
@keyframes bth-anim1{
	0%{
		left: -100%;
	}
	50%,100%{
		left: 100%;
	}
}
.login-box a span:nth-child(2){
	top: -100%;
	right: 0;
	width: 2px;
	height: 100%;
	background: linear-gradient(180deg, transparent,#03e9f4);
	animation: bth-anim2 1s linear infinite;
	animation-delay:.25s ;
}
@keyframes bth-anim2{
	0%{
		top: -100%;
	}
	50%,100%{
		top: 100%;
	}
}

.login-box a span:nth-child(3){
	bottom: 0;
	right: -100%;
	width: 100%;
	height: 2px;
	background: linear-gradient(270deg, transparent,#03e9f4);
	animation: bth-anim3 1s linear infinite;
	animation-delay:.5s ;
}
@keyframes bth-anim3{
	0%{
		right: -100%;
	}
	50%,100%{
		right: 100%;
	}
}

.login-box a span:nth-child(4){
	bottom: -100%;
	left: 0;
	width: 2px;
	height: 100%;
	background: linear-gradient(360deg, transparent,#03e9f4);
	animation: bth-anim4 1s linear infinite;
	animation-delay: ;
}
@keyframes bth-anim4{
	0%{
		bottom: -100%;
	}
	50%,100%{
		bottom: 100%;
	}
}
